A look back at the London smog of 1952 and the half century since. (Guest Editorials).

The modern field of environmental health owes much to the tragedy that befell Greater London, some 50 years ago this month. From 5 December through 9 December 1952 a heavy, motionless layer of smoky, dusty fumes from the region's million or more coal stoves and local factories settled in the London basin. This thick sulfurous smoky fog, the "smog," brought traffic and people to a standstill. Not all medical and political authorities appreciated what was happening, but the undertakers and florists knew there was a problem. They ran out of caskets and flowers.

Health officials at the time did not appreciate the magnitude or severity of the problem, having previously weathered many dense "pea-souper" fogs and smogs. This fog became known as the Big Smoke because its toll and the public reactions to it were without precedent. Hospital admissions, pneumonia reports, applications for emergency bed service, and mortality followed the peak of air pollution. Mortality remained elevated for a couple of months after the fog. A preliminary report, never to be finalized, attributed these later deaths to an influenza epidemic. New evidence shows that this could not be the case and that only a fraction of the deaths could be from influenza. Davis (2002) leaves 12,000 unexplained and additional deaths during the episode and in the two months after the peak fog ebbed (Bell and Davis 2001).

Happily for Londoners, air quality is now much better, with mean annual P[M.sub.10] levels (particulate matter [less than or equal to] 10 [micro]m in aerodynamic diameter) closer to 30 [micro]g/[m.sup.3] than the 300 [micro]g/[m.sup.3] 50 years ago (and approximately 3,000 [micro]g/[m.sup.3] in December 1952). However, risks from air pollution remain. In London, coal stoves are all but gone, but transport is the overwhelming source of PM and N[O.sub.x] emissions. One recent estimate attributed 380 premature fatalities and 350 respiratory hospital admissions per year to emissions from from transport in London (Greater London Authority 2002). In a major collaborative study in Europe overall, Kunzli et al. (2000) calculated that the net impact on health from pollution tied with transport was greater than that associated with traffic crashes alone.

These tragic public events in London half a century ago spurred the realization that polluted air could not only cause an immediate increase in deaths and illness but could also result in longer-term and more subtle effects. Numerous studies in EHP and elsewhere have provided a rich encyclopedia of studies, showing a wide range of health impacts ranging from increased death rates in infants and the elderly to a host of chronic respiratory and cardiac ailments, as well as low birth weight, impaired development, and cancer.

The evidence that even relatively low levels of air pollution have serious long-term effects has been reinforced by a number of recent reports. The ongoing study of nearly a quarter million volunteers begun by the American Cancer Society has recently revealed that those who live in more polluted areas have significantly higher risks of lung cancer (mortality relative risk of 1.14 for a 10 [micro]g/[m.sup.3] increase of P[M.sub.2.5]) as well as greater risks of cardiopulmonary mortality (Pope et al. 2002). A Dutch cohort study provides additional evidence of long-term effects tied to chronic exposures, again on cardiorespiratory deaths (Hoek et al. 2002). The benefits of reducing particulates tied with the burning of coal have recently been demonstrated in Ireland (Clancey et al. 2002). A decade after Dublin banned all burning of bituminous coal, black smoke concentrations have decreased 70%, deaths from respiratory causes have dropped 15.5%, and cardiovascular deaths have fallen 10.3%. This amounts to about 116 fewer respiratory deaths and 243 fewer cardiovascular deaths per year in Dublin after the ban (Clancey et al. 2002).

Thus, the London story is not merely historic. Conditions in some rapidly developing countries today can come eerily close to those of London, either indoors or outdoors. Although coal stoves are not generally the problem, biomass fuels, garbage, and other incompletely burned organic materials often cause unhealthy conditions inside homes and factories throughout the world. For example, in 1995 the mean annual concentration of total suspended particulates was 800 [micro]g/[m.sup.3] in Lanzhou, China, and > 400 [micro]g/[m.sup.3] in Delhi, India.

Women in some rural regions of India, Africa, and China are currently developing lung cancer and respiratory ailments at rates typically found in smokers because of their chronic exposures to indoor smoky fuels. In Teheran, Iran, in 1999, hospitals and clinics overflowed with cardiac patients as the city struggled with one of its worst health emergencies. Among the many serious problems of the Middle East and Asia, air pollution is one for which the causes are known and treatable.

This information is driving major shifts in public policy in both developing and developed countries. Choice of fuels is now recognized as a major influence on public health as well as a driving factor in development worldwide. Fifty years after the London episode, we need to reconcile aspirations to maintain or expand economies with the problem of reliance on inefficient, polluting, and greenhouse gas-emitting fuels. The lessons of London remain pertinent today as countries grapple with major policy choices on energy and transport.

Devra L. Davis
Carnegie Mellon University
Pittsburgh, Pennsylvania
E-mail: [e-mail]

Michelle L. Bell
Johns Hopkins University
Baltimore, Maryland

Tony Fletcher
London School of Hygiene and Tropical Medicine
London, United Kingdom

Devra Davis is an epidemiologist and researcher on the environmental causes of breast cancer and chronic disease. She was recently named an honorary professor at the London School of Hygiene and Tropical Medicine, and she is an adviser to the World Health Organization. Her book, When Smoke Ran Like Water, was awarded a medal as a finalist in nonfiction by the National Book Awards

Michelle Bell is an environmental engineer who studies air pollution, public health, and related policy implications. She recently received her Ph.D. from Johns Hopkins University.

Tony Fletcher is an epidemiologist whose current research interests are health effects of air pollution and arsenic-contaminated drinking water. He is the lead organizer of the "Big Smoke" anniversary conference commemorating the Great Smog of 1952 in London.

REFERENCES

Bell ML, Davis D. 2001. Reassessment of the lethal London fog of 1952: novel indicators of acute and chronic consequences of acute exposure to air pollution. Environ Health Perspect 109(suppl 3):389-394.

Clancey L, Goodman P, Sinclair H, Dockery DW. 2002. Effect of air-pollution control on death rates in Dublin, Ireland: an intervention study. Lancet 360:1210-1214.

Davis DL. 2002. When Smoke Ran Like Water. New York:Basic Books.

Greater London Authority. 2002. Cleaning London's Air: Highlights of the Mayor's Air Quality Strategy. Available: http://www.london.gov.uk/approot/mayor/strategies/ air_quality/fin_docs/highlights.pdf [accessed 6 November 2002].

Hoek G, Brunekreef B, Goldbohm S, Fischer P, van den Brandt PA. 2002. Association between mortality and indicators of traffic-related air pollution in the Netherlands: a cohort study. Lancet 360:1203-1209.

Kunzli N, Kaiser R, Medina S, Studnicka M, Chanel O, Filliger P, et al. 2000. Public-health impact of outdoor and traffic-related air pollution: a European assessment. Lancet 356:795-801

Pope CA, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K, et al. 2002. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA 287:1132-1141.